1. Field of the Invention
The present invention relates to a device for starting the engine of model jet airplanes such as small gas turbines, in particular, the present invention represents a starting device for starting up of model jet engines such as small gas turbines as they are especially utilized in propulsion of model airplanes.
2. Description of the Prior Art
For the starting, especially start-up of these model gas turbines, various procedures have been known in the prior art. These include the following:
A. Starting by means of compressed air.
To attain the start up, especially the required revolutions per minute rate of the turbine, the running system of the gas turbine is brought to the necessary rate of revolutions per minute by means of highly compressed air. The compressed air necessary for this procedure is made available in practice mostly by means of compressed air tanks (such as scuba diver tanks). The disadvantage of this method consists in the fact that in the hobby utilization of the gas turbine the relatively heavy and bulky pressed air tank must be carried along. Also, the possible number of starts is reduced by the limited availability of compressed air. When the compressed air tank is empty, no further starts are possible, and the tank must be refilled by a service provider (specialized store or scuba shop). In addition, the compressed air tank musts be regularly evaluated and re-certified.
B. Startup by means of a blowing device such as a fan.
In this method, the turbine running system is triggered by means of a fan providing accelerated air to bring it to the required revolutions per minute. The air accelerated by the mostly electrically propelled fan is blown into the turbine entry and thus sets the running system of the turbine in rotation. The disadvantage of this method consists in the fact that the air stream/flow generated by the fan must be introduced to the turbine opening in a relatively large cross section (through a very large access hole). This creates in fact the need for a free access to the turbine such as turbine intake. However, this is difficult if not impossible to realize in the construction of turbines in model airplanes. A firm installation of the fan directly in front of the turbine is in many cases excluded, as after the start of the turbine the air supply is impeded by the starting fan which is always located in the stream of the airflow.
Moreover, it is necessary to cool the turbine immediately after shut off in order to avoid damage through overheating of the very expensive high velocity devices (such as the rotor assembly and bearings). This cooling procedure is hitherto also carried out by means of subjection of the turbine to compressed air or a fan (i.e. cooling air is blown through the turbine). But in the case of a remote landing of the model airplane, the cooling procedure is often impossible to carry out immediately after the shutting off of the turbine, and bearing damages through overheating are quite likely.
The present invention involves a starting procedure for model jet engines, which overcomes the above mentioned insufficiencies and disadvantages, and provide a secure and simply accessible start up for model jet engines, as well as to facilitate an immediate cooling after the turning off of the turbine.